There is a known image processing apparatus for determining to which of an edge section, a flat section, and a gradation section a pixel of interest in an image belongs (refer to, for example, PTL 1). In PTL 1, a block composed of a pixel of interest and pixels adjacent to the pixel of interest is set in an image, a spatial frequency included in the block is calculated by applying discrete cosine transformation to the pixel values in the block, and, on the basis of the spatial frequency, it is determined to which of an edge section, a flat section, and a gradation section the pixel of interest belongs.